1. Field of the Invention
The present invention relates to a lever-type hoist and more particularly to a lever-type hoist which is capable of instant idling without resort to manipulating an operating wheel for initiation of idling.
2. Description of the Related Art
As a lever-type hoist, the present applicant previously proposed one disclosed in Japanese Patent Kokai H10-59689.
The above lever-type hoist is a hoisting device wherein a pressure receiving member rigidly secured to a drive shaft is rotated by a press drive member through a reverse rotation stop ring and a pair of friction members disposed on both sides of said stop ring, with a left hand coil spring being interposed between said pressure receiving member and said press drive member as a unit to apply a biasing torque in the direction releasing the pressing force of the press drive member on the pressure receiving member.
Now, said pressure receiving member is formed with an axially forwardly opening boss hole and said boss hole is formed with a radially outwardly extending rectangular first engaging groove. Furthermore, as shown in FIG. 6, said press drive member A is formed with a spring loading hole B opening at the axially base side and the spring loading hole is formed with a second engaging groove C extending radially outward. Therefore, the base end portion of the coil spring is inserted into the boss hole with its base end engaging portion engaged with the first engaging groove of the pressure receiving member, and the tip end portion of the coil spring is inserted into the spring loading hole with its tip end engaging portion E of the coil spring D engaged with the second engaging groove of the press drive member.
However, in the case of the conventional hoist, both the angle formed between the wind-up side surface of the first engaging groove and the axially forward surface of the pressure receiving member and the angle formed between the wind-down side of the second engaging groove and the axially backward surface of the press drive member are a right angle. For instance, FIG. 7 illustrates a section of the second engaging groove C of the press drive member A and as shown, the angle formed between the wind-down side C1 of the second engaging groove and the axially backward surface F of the press drive member is a right angle.
Thus, in the conventional hoist, since said angles are made a right angle or more than 90.degree., the base end engaging portion or the tip end engaging portion formed at each end of the coil spring is sometimes located at the tip of the engaging surface. Therefore, there is a fear that since said each engaging portion of the coil spring is disengaged from said tip of the engaging surface when an impact is applied to an operating handle, etc., a counterclockwise rotational force of the spring does not apply to the press drive member and the lever-type hoist cannot run idle.
The present invention has been made to overcome the above-mentioned disadvantages.